Power switching arrangement

ABSTRACT

A circuit protection system for a power panel is disclosed. The circuit protection system includes a transistor connected in a channel of a power panel, the transistor connected between return connections of a load and a return path, and the power panel including a plurality of channels connected to the load. The circuit protection system also includes control circuitry electrically connected in parallel with the transistor, the control circuitry configured to selectively activate the transistor to allow current to pass through the transistor based on an observed voltage across the transistor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/576,394,filed Oct. 9, 2009, which application claims priority to U.S.Provisional Patent Application Ser. No. 61/104,169, filed Oct. 9, 2008,which applications are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates generally to power distribution systems;more specifically, the present disclosure relates to a power switchingarrangement.

BACKGROUND

Electrical circuit panels such as power distribution panels typicallyinclude a number of different circuit elements such as fuse holders andfuses, circuit breakers, input and output connectors and alarm signalLED's. For safety and other reasons, the electrical circuits of powerdistribution panels are enclosed within a housing structure. Therefore,the circuit elements listed above have typically been inserted intoholes that have been pre-cut or pre-punched into the housing structure,usually on a front or back panel of the housing structure.

These prior circuit panels are fixed and once the holes are formed inthe housing, the type and arrangement of the components is limited. Inorder to manufacture different fixed circuit panels of the priorsystems, a circuit panel manufacturer would punch out different patternsof holes in the front or back panels of the housing structure in orderto accommodate different arrangements of circuit elements. Significantretooling time and costs are involved for offering different fixedpanels. Assembly of the circuit elements is also difficult when theelements are inserted through holes. One solution is described and shownin U.S. Pat. No. 6,456,203.

In addition, such panels are hardwired between the input and outputconnections, and the fuse and/or breaker locations. In some panels,redundant power connections are provided, controlled by an OR-ing diodeincluding a heat sink. These features can take up significant spacewithin the panel, and can result in current passing through OR-ingdiodes associated with inactive power connections.

There is a continued need for improved power distribution panels.

SUMMARY

In accordance with the present disclosure, a power switching arrangementis disclosed. The power switching arrangement includes a protectioncircuit that selectively switches to allow or block return current in apower distribution unit based on sensed voltages.

According to a first aspect, a circuit protection system for a powerpanel is disclosed. The circuit protection system includes a transistorconnected in a channel of a power panel, the transistor connectedbetween return connections of a load and a return path, and the powerpanel including a plurality of channels connected to the load. Thecircuit protection system also includes control circuitry electricallyconnected in parallel with the transistor, the control circuitryconfigured to selectively activate the transistor to allow current topass through the transistor based on an observed voltage across thetransistor.

According to a second aspect, a power panel useable in a powerdistribution system is disclosed. The power panel includes a pluralityof channels, with each channel including a supply path and a returnpath. The return path is electrically connectable through the powerpanel to return connections of a load. The power panel also includes acircuit protection system associated with one of the plurality ofchannels. The circuit protection system includes a transistor connectedbetween the return connections and the return path. The circuitprotection system also includes control circuitry electrically connectedin parallel with the transistor, the control circuitry configured toselectively activate the transistor to allow current to pass through thetransistor based on an observed voltage across the transistor.

According to a third aspect, a method of providing circuit protection ina power distribution panel is disclosed. The method includes sensing avoltage above a threshold across a transistor connected between a returnpath and return connections configured to receive connections to a load.The method further includes, upon sensing the voltage above a thresholdacross the transistor, activating the transistor with control circuitryconnected in parallel with the transistor.

According to a fourth aspect, a power panel is disclosed. The powerpanel includes a chassis including a top, a bottom, a front, a rear, andtwo sides. The power panel further includes a plurality of power inputconnections on the chassis, each power input connection including asource input connection and a return input connection. The power panelalso includes a plurality of power output connections on the chassis,each of the power output connections including a source outputconnection and a return output connection, and each of the power outputconnections connected to a power input connection through the chassis.The power panel includes a protection circuit connected between at leastone of the power output connections and a power input connection. Theprotection circuit includes a transistor connected between the returnoutput connection and the return input connection, and control circuitryelectrically connected in parallel with the transistor, the controlcircuitry configured to selectively activate the transistor to allowcurrent to pass through the transistor based on an observed voltageacross the transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front, top, and right side perspective view of oneembodiment of a power distribution panel in accordance with the presentinvention.

FIG. 2 is a rear, top, and left side perspective view of the powerdistribution panel of FIG. 1.

FIG. 3 is a front view of the power distribution panel of FIG. 1.

FIG. 4 is a right side view of the power distribution panel of FIG. 1.

FIG. 5 is an exploded front, top, and right side perspective view of thepower distribution panel of FIG. 1.

FIG. 6 is an exploded front, top, and left side perspective view of thepower distribution panel of FIG. 1.

FIG. 7 is a top view of the power distribution panel of FIG. 1, shownwith a top cover portion removed.

FIG. 8 is a front view of the chassis of the power distribution panel ofFIG. 1, shown without modules.

FIG. 9 is perspective view of a first circuit module.

FIG. 10 is a top view of the first circuit module.

FIG. 11 is a bottom view of the first circuit module.

FIG. 12 is a front view of the first circuit module.

FIG. 13 is a right side view of the first circuit module.

FIG. 14 is an exploded perspective view of the first circuit module.

FIG. 15 is a perspective view of a second circuit module.

FIG. 16 is a top view of the second circuit module.

FIG. 17 is a bottom of the second circuit module.

FIG. 18 is a front view of the second circuit module.

FIG. 19 is a right side view of the second circuit module.

FIG. 20 is an exploded perspective view of the second circuit module.

FIG. 21 is a front, top, and right side perspective view of a secondembodiment of a power distribution panel in accordance with the presentinvention.

FIG. 22 is a rear, top, and left side perspective view of the powerdistribution panel of FIG. 21.

FIG. 23 is a front view of the power distribution panel of FIG. 21.

FIG. 24 is a right side view of the power distribution panel of FIG. 21.

FIG. 25 is an exploded front, top, and right side perspective view ofthe power distribution panel of FIG. 21.

FIG. 26 is an exploded front, top, and left side perspective view of thepower distribution panel of FIG. 21.

FIG. 27 is a top view of the power distribution panel of FIG. 21, shownwith a top cover portion removed.

FIG. 28 is a front view of the chassis of the power distribution panelof FIG. 21, shown without modules.

FIG. 29 is a front, top, and right side perspective view of a thirdembodiment of a power distribution panel in accordance with the presentinvention.

FIG. 30 is a front, bottom, and right side perspective view of the powerdistribution panel of FIG. 29.

FIG. 31 is a front perspective view of a first circuit module of thepower distribution panel of FIG. 21.

FIG. 32 is a rear perspective view of the first circuit module of FIG.31.

FIG. 33 is a front view of the first circuit module of FIG. 31.

FIG. 34 is a side view of the first circuit module of FIG. 31.

FIG. 35 is a top view of the first circuit module of FIG. 31.

FIG. 36 is a bottom view of the first circuit module of FIG. 31.

FIG. 37 is a cross-sectional view of the first circuit module of FIG.31, taken along lines 37-37 of FIG. 35.

FIG. 38 is an enlarged view of a portion of the first circuit module ofFIG. 37, shown partially connected to a backplane connector.

FIG. 39 is an exploded front perspective view of the first circuitmodule of FIG. 31.

FIG. 40 is a front perspective view of a second circuit module of thepower distribution panel of FIG. 21.

FIG. 41 is a rear perspective view of the second circuit module of FIG.40.

FIG. 42 is a front view of the second circuit module of FIG. 40.

FIG. 43 is a side view of the second circuit module of FIG. 40.

FIG. 44 is a top view of the second circuit module of FIG. 40.

FIG. 45 is a bottom view of the second circuit module of FIG. 40.

FIG. 46 is a cross-sectional side view of the second circuit module ofFIG. 40, taken along lines 46-46 of FIG. 44.

FIG. 47 is an enlarged view of a portion of the second circuit module ofFIG. 46, shown partially connected to a backplane connector.

FIG. 48 is an exploded perspective view of the second circuit module ofFIG. 40.

FIG. 49 is a flow chart relating to the voltage disconnect monitor.

FIG. 50 shows greater detail of a front of a power distribution panelincluding two of the first circuit modules of FIG. 31, including thelabel configurations.

FIG. 51 shows greater detail of a front of the power distribution panelof FIG. 21, including the label configurations.

FIG. 52 shows in greater detail a front of another power distributionpanel including four of the second circuit modules of FIG. 40, includingthe labeling configurations.

FIG. 53 shows a schematic view of a power distribution circuit used inthe power distribution panels of the present disclosure.

FIG. 54 shows a schematic view of a protection circuit used in the powerdistribution panels of the present disclosure.

DETAILED DESCRIPTION

Referring to FIGS. 1-7, a power distribution system or panel 10 isshown. Power distribution system 10 is a modular design including apanel construction having a chassis 12 and at least one removablecircuit module 14. In the illustrated embodiment, one first circuitmodule 16, and two second circuit modules 18 are shown. First circuitmodule 16 is positioned in a left side of chassis 12 wherein the firstcircuit module 16 is of a first design. Two second circuit modules 18are also shown positioned in a right side of chassis 12 wherein secondcircuit modules 18 are of a different design from first circuit module16.

Each circuit module 14 includes circuit distribution components. In thepreferred embodiment, the circuit distribution components include acircuit protection device, such as a fuse or a breaker, and a poweroutput arrangement 60. System 10 includes a power input arrangement 50wherein the circuit protection devices within the modules 14 protect thecircuit between the power input arrangement 50 and the power outputarrangement 60.

Referring also to FIG. 8, chassis 12 includes a top 30, a spaced apartbottom 32 and opposite sides 34, 36. Adjacent to sides 34, 36 arebrackets 38 for mounting to a rack, cabinet, or other telecommunicationsequipment. Chassis 12 includes a rear 40. Chassis 12 defines an interior42 having an open front 44. Chassis interior 42 in the illustratedembodiment includes a first module receiving area 46 on a left side ofchassis 12, and a second module receiving area 48 on a right side ofchassis 12. A central area 49 of chassis 12 is provided. In someembodiments, central area 49 can be used for alarming and/or systemmanagement components.

Panel 10 includes power input connectors or terminals 50 connected tointernal bus bars 52. A backplane 54, such as a printed circuit board,is positioned adjacent to rear 40 of chassis 12. Bus bars 52 connectinput connectors 50 to backplane 54. Modules 16, 18 interconnect withbackplane 54 to enable power distribution through modules 16, 18. Eachmodule 16, 18 includes at least one power output connector 60, and acircuit protection device 62, such as a fuse or a breaker.

As shown in FIG. 7, bus bars 52 are generally Z-shaped metallic barsextending from first ends 68 to opposite ends 70. Opposite ends 70define dual contact points 72 which can be mounted with fasteners (notshown) to backplane 54 to electrically interconnect bus bars 52 andbackplane 54. Ends 68 of bus bars 52 are mounted to input terminals 50at input terminal mounts 76 of chassis 12.

Interior 42 of chassis 12 includes side supports 80 and central support82. Side supports 80 and central support 82 include a plurality ofmodule guides 84 which define longitudinal slots for receipt oflongitudinal rails of each of modules 16, 18. Central support 82 definesan interior for receiving an alarm card 92. Alarm card 92 mounts toalarm card connector 93 on backplane 54. Alarm card 92 is optional ifsuch functionality is employed by panel 10.

Each module 16, 18 includes a rear module connector 96. Backplane 54includes a front face 100, and opposite rear face 102. Positioned onfront face 100 are a plurality of mating connectors 104 for electricallyconnecting to the module connectors 96.

Referring now in greater detail to FIGS. 9-14, first circuit module 16is shown. Module 16 includes a frame 200 including a base 202, and afront tray 204 with a front lip 206. A vertical support 208 extends upfrom base 202 and defines a plurality of openings 210, 212 for outputterminal units 220, and fuses 222, respectively. Base 202 also includessides 226 and longitudinal rails 228. A printed circuit board 230connects between module connector 96 and the circuit elements includingoutput terminal units 220 and fuses 222. Fuse holder or block 240 withfuses 222 is held in place by a support tray 241 and a strap 242.

Referring now to FIGS. 15-20, one of the second circuit modules 18 isshown. Second module 18 includes a frame 300 including a base 302, afront tray 304, and a front lip 306. A vertical support 308 defines aplurality of openings 310, 312 for output terminal units 320 and fuses322, respectively. Frame 300 includes sides 326, and longitudinal rails328. A printed circuit board 330 connects between module connector 96and the circuit elements including output terminal units 320 and fuses322.

Modules 16, 18 mount to chassis 12 with fasteners (not shown) throughholes 238, 338 in each module, and holes 66 in supports 80 of chassis12. Front trays 204, 304 are provided for cable management of the poweroutput cables. Front lips 206, 306 also provide a convenient grippingsurface.

Because of the modular design for chassis 12 and modules 16, 18, repairor replacement of parts is facilitated. Should upgrades becomedesirable, new modules can be provided. The modules also allow fordistributed control functions, such as in the case of redundant (dualfeed) applications. The OR-ing diodes or other controllers can belocally placed on each module. Details regarding possible circuitry usedis described below in conjunction with FIGS. 53-54.

Each module includes the desired circuit protection components. Module16 in the illustrated embodiment is a TPA type fuse. Modules 18 are GMTtype fuses. Other fuse types or breakers can be used.

Referring now to FIGS. 21-52, further embodiments of power distributionsystems or panels similar to panel 10 are shown. In FIGS. 21-28, asimilar panel 410 is shown having a chassis 412, a first circuit module416, and two second circuit modules 418. Alternatively, panel 410 canhold two first circuit modules 416, or four second circuit modules 418.

Chassis 430 includes air flow openings 440 on a top 430, and on a bottom432. Chassis 430 further includes a forward facing ground 442 on top430.

As with panel 10, first circuit module 416 and second circuit modules418 are removable from chassis 430. Module 416 in the illustratedembodiment is a TPA type fuse with four fuses instead of two as noted inpanel 10. Modules 318 are GMT type fuses, each including four fuses,instead of three as noted above for modules 18.

Referring now to FIGS. 26-28, a baffle plate 480 is shown mounted to abottom 432 of chassis 430. Baffle plate 480 is spaced from bottom 432 byspacers 481 so as to allow airflow communication with openings 440 inbottom 432. Baffle plate 480 also functions as an airflow blocker toblock warm air from below chassis 430 from entering into chassis 430,such as from heat emitting equipment mounted below.

Referring now to FIGS. 29 and 30, a further embodiment of a panel 510 isshown. Panel 510 includes the same chassis 430 as for panel 410, andfour second modules 418, two on each side. Panel 510 also is shownincluding baffle plate 480. Baffle plate 480 also includes a front lip482 positioned in an upward direction relative to a remainder of baffleplate 480. Front lip 482 and the rest of baffle plate 480 can alsofunction as a cable tray for holding cables extending to and from panel510, or for cables extending between equipment on either side of panel510.

Referring now to FIGS. 31-39, first module 416 is shown in greaterdetail. Module 416 includes a frame 600 including a base 602, and afront tray 604 with front lips 606. Front tray 604 includes perforations607 for use with cable ties. A vertical support 608 extends up from base602 and defines a plurality of openings 610, 612 for output terminalunits 620, and fuses 622, respectively. Base 602 also includes sides 626and longitudinal rails 628. Two printed circuit boards 630, 631 connectbetween module connectors 696 and the circuit elements including outputterminal units 620 and fuses 622. Fuse holder or block 640 with fuses622 is held in place by a support tray 641 and a strap 642. Variousopenings 646 are provided in base 602 and tray 641 to assist withventilation.

Referring now to FIGS. 40-48, second module 418 includes a frame 700including a base 702, and a front tray 704 with front lips 706. Similarperforations 707 are provided for use as cable ties in front tray 704. Avertical support 708 defines a plurality of openings 710, 712 for outputterminal units 720 and fuses 722 respectively. Frame 700 includes sides726, and longitudinal rails 728. A printed circuit board 730 connectsbetween module connector 696 and the circuit elements including outputterminal units 720 and fuses 722. Various openings 746 are provided inbase 702 to assist with ventilation.

Referring now to FIGS. 38, 47, and 49, a voltage disconnect feature isillustrated. One issue that can arise with removing of a module duringoperation is that arcing may occur between the connectors 696 of themodules, and the connectors 104 of the backplane. A voltage disconnectsystem 800 is provided to turn off the power to the module prior toremoval of the module in order to prevent arcing. A selected pin 808among pins 806 of connector 696 is provided with a shortened length. Theshortened pin 808 will disengage first before the power connectionsdisengage. This will provide an interrupt signal that will be receivedby a device, such as a microcontroller or a similar device on themodule, to activate a voltage disconnect mechanism which turns off thecurrent to the load. This will prevent arcing on the connectors andprevent damage from occurring. Furthermore, if the module is notcompletely inserted, the short pin 808 will prevent the voltagedisconnect mechanism from activating and keep the output current turnedoff until the module is fully inserted. A visual indication will bedisplayed if the module is not fully inserted. FIG. 49 illustrates anexample flow chart illustrating the voltage disconnect feature.

Each module 416, 418 includes various visual indicators to indicatesystem conditions. For example, there are provided visual indicationsfor power, low voltage, blown fuse, and excess temperature throughvisual indicators 900.

Power input covers 910, and power output covers 920 can be provided ifdesired.

As shown in FIGS. 50-52, various arrangements for panels 410, 510, 1010are shown using the same chassis 430. Labels 1200, 1210, 1220 can beused to label each module 416, 418 as needed for each arrangement.Labels 1200, 1210, 1220 can be adhesively attached to each module 416,418 as needed.

Although FIGS. 1-52 describe certain configurations for a powerdistribution panel, it is understood that additional types of powerdistribution panels can be used as well. For example, other types ofpanels can be used, such as those described in U.S. patent applicationSer. No. 11/654,367, filed Jan. 17, 2007, the disclosure of which ishereby incorporated by reference in its entirety.

Now referring to FIGS. 53-54, load protection circuits are shown thatcan be implemented in the power distribution units and panels of thepresent disclosure. FIG. 53 illustrates a power distribution circuit1000 in which a power distribution unit can be used, according to apossible embodiment of the present disclosure. The power distributioncircuit 1000 includes a power distribution unit 1010 including at leasttwo power channels 1020, 1030. Each of the power channels 1020, 1030 areshown to be connected to load equipment 1040, which includes a loaddevice 1050 and protection diodes 1060, 1070.

Each of the power channels 1010, 1020 includes a negatively polarizedsupply path and a positively polarized return path. In the embodimentshown, power channel 1010 includes a supply path A1− and return pathA1+, and power channel 1020 includes supply path B1− and return pathB1+. For each of the power channels, the supply path (e.g. A1−, B1−)connects to a low voltage disconnect circuit 1080 and a fuse 1090, whichprotect the load equipment 1040 from unexpected power distributionevents. In the embodiment shown, the low voltage disconnect circuit 1080disconnects the channel from supplying a voltage lower than the rated orexpected voltage to be supplied to the load equipment 1040. The fuse1090 prevents overcurrent events from reaching the load equipment. Othercircuit protection equipment can be included at the supply path of eachchannel as well.

At the return path A1+, B1+ of each power channel 1020, 1030, aswitching circuit 1100 selectively allows current to pass in a singledirection, such that current flow from a battery (not shown) connectedto each channel in a reversed direction (i.e. with a positive terminalconnected to the supply path A1− or B1− and a negative terminalconnected to the return path A1+ or B1+) is blocked. The switchingcircuit 1100 also prevents return path current existing on a return pathwhen the corresponding supply path (and overall channel) is inactive.For example, the switching circuit 1100 prevents current on path B1+when channel 1030 is inactive but channel 1020 is active, and preventscurrent on path A1+ when channel 1020 is inactive but channel 1030 isactive.

FIG. 54 illustrates details of the switching circuit 1100. The switchingcircuit 1100 acts as a circuit protection system for a powerdistribution panel, and, in certain embodiments, represents an“active-OR” circuit arrangement. The switching circuit 1100 connects toa plurality of return connections 1110 from a load (e.g. load equipment1040 of FIG. 53), which are consolidated as a return path 1120 (e.g.path A1+ or B1+ of FIG. 53) of the power distribution circuit. Thereturn path 1120 is connected to a return, or positive, terminal of abattery or other power supply. The switching circuit 1100 includes oneor more transistors, shown as MOSFET devices 1130, which are arranged inseries. Each device 1130 has a source 1132, drain 1134, gate 1136, and abody diode 1138. The devices 1130 are connected in parallel, with allsources 1132 interconnected to the return path 1120, all drains 1134interconnected to the return connections 1110, and all gates 1136interconnected. In the embodiment shown, the MOSFET devices 1130 areN-Channel enhanced MOSFET devices; however, P-Channel MOSFET devices orother types of high-current, low voltage-drop devices are useable aswell.

A control circuit 1150 selectively activates the MOSFET devices based onsensed voltages at the return connections 1110 and return path 1120. Thecontrol circuit includes two sensing pins 1152, 1154 (shown as SENSE+and SENSE−, respectively), and a control pin 1156. Sensing pin 1152detects the voltage at the return path 1120, and pin 1154 detectsvoltage at the return connections 1110. The control pin 1156 connects tothe interconnected gates 1136, and acts to selectively activate theMOSFET devices 1130 based on the voltages sensed at the sensing pins1152, 1154.

In operation, the circuitry of FIGS. 53-54 is arranged for high currentapplications. For example, depending upon selection of specificcomponents for use in the switching circuit 1100, the circuitry cansupport approximately 75-125 amps of current passing through eachchannel of the power distribution panel.

In operation, when the channel associated with the switching circuit1100 is inactive, the body diodes 1138 in the MOSFET devices 1130operate similarly to a Schottky diode to prevent current flow if thevoltage difference between the return connections 1110 and the returnpath 1120 is below a forward voltage determined by the characteristicsof the Schottky diode. The forward voltage of the body diodes 1138 ispreferably selected to be higher than is generally used in similar powerapplications (typical Schottky diodes used in similar applications havea forward voltage of approximately 0.35 V). In certain embodiments, thebody diode 1138 has a forward voltage of about 0.45 V to about 2 V. Incertain applications, the forward voltage of the body diode is about 0.9V to about 1.2 V. The higher voltage for the body diode 1138, inconjunction with the presence of four paralleled MOSFET devices 1130,helps to prevent current from flowing in the return path when the moduleis powered down. This is at least in part due to the fact thatsubstantial additional energy is required to forward bias the multiplebody diodes of greater voltage, as compared to a single, lower voltagebody diode.

The higher voltage drop corresponds to a large amount of heatdissipation when the devices 1130 are used in a high currentapplication, such as a power panel. Due to this high current passingthrough the devices 1130, the MOSFET devices are activated duringoperation, to reduce the voltage drop across the devices to a fewmillivolts, thereby significantly reducing the heat dissipation at eachMOSFET device. Incorporating additional MOSFET devices 1130 allowsfurther separation of heat dissipating elements during circuitoperation.

When a negative voltage condition such as either a reverse batterycondition (e.g. the voltage across sensing pins 1152, 1154 is reversed)or a voltage difference is detected across two battery sources (e.g.where the voltage source associated with the channel having switchingcircuit 1100 has a lower voltage than another channel connected to theload) is sensed, the control circuit 1150 deactivates the MOSFET devices1130, causing the body diodes 1138 to block the reverse battery currentfrom flowing to the load device connected to the channel associated withthe circuit 1100 (e.g. as seen in FIG. 53).

Although the switching circuit 1100 is shown using four MOSFET devices1130, more or fewer devices can be included in the circuit. Additionaldevices could provide more redundancy/failsafe characteristics, and canact to divide down the current load passing through each device. Theadditional devices can also provide improved thermal characteristics,possibly allowing for exclusion of a heatsink from the MOSFET devices.Furthermore, it is preferable that each of the MOSFET devices 1130 isindividually rated to have sufficient current capacity to pass all ofthe possible current from the return connections 1110 to the return path1120.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

1-23. (canceled)
 24. A circuit protection system for a power panel, thesystem comprising: a transistor connected in a channel of a power panel,the transistor connected between return connections of a load and areturn path, the power panel including a plurality of channels connectedto the load; and control circuitry electrically connected in parallelwith the transistor, the control circuitry configured to selectivelyactivate the transistor to allow current to pass through the transistorbased on an observed voltage across the transistor.
 25. The circuitprotection system of claim 24, further comprising a plurality oftransistors connected in parallel between the return connections and thereturn path.
 26. The circuit protection system of claim 24, wherein thetransistor is a MOSFET transistor.
 27. The circuit protection system ofclaim 26, wherein the MOSFET transistor is an enhanced MOSFETtransistor.
 28. The circuit protection system of claim 24, wherein thetransistor includes a body diode.
 29. The circuit protection system ofclaim 28, wherein the body diode has a forward voltage of at leastapproximately 0.45 V.
 30. The circuit protection system of claim 24,wherein the control circuitry includes a control signal connected to agate of the transistor.
 31. The circuit protection system of claim 30,wherein the control circuitry is configured to activate the gate duringuse of the channel by the load.
 32. The circuit protection system ofclaim 30, wherein the control circuitry is configured to deactivate thegate upon detecting a reverse battery condition in the channel.
 33. Thecircuit protection system of claim 30, wherein the control circuitry isconfigured to deactivate the gate upon detecting a negative voltagecondition in the channel.
 34. A power panel useable in a powerdistribution system, the power panel comprising: a plurality ofchannels, each channel including a supply path and a return path, thereturn path electrically connectable through the power panel to returnconnections of a load; and a circuit protection system associated withone of the plurality of channels, the circuit protection systemincluding: a transistor connected between the return connections and thereturn path; control circuitry electrically connected in parallel withthe transistor, the control circuitry configured to selectively activatethe transistor to allow current to pass through the transistor based onan observed voltage across the transistor.
 35. The power panel of claim34, further comprising a plurality of circuit protection systems, eachcircuit protection system associated with a different one of theplurality of channels.
 36. The power panel of claim 34, wherein eachcircuit protection system includes a plurality of transistors connectedin parallel between the return connections and the return path.
 37. Thepower panel of claim 34, wherein the control circuitry has a controlsignal connected to a gate of the transistor.
 38. The power panel ofclaim 37, wherein the control circuitry is configured to activate thegate during use of the channel by the load.
 39. The power panel of claim37, wherein the control circuitry is configured to deactivate the gateupon detecting a reverse battery condition in the channel.
 40. The powerpanel of claim 37, wherein the control circuitry is configured todeactivate the gate upon detecting a negative voltage condition in thechannel.
 41. A method of providing circuit protection in a powerdistribution panel, the method comprising: sensing a voltage above athreshold across a transistor connected between a return path and returnconnections configured to receive connections to a load; and uponsensing the voltage above a threshold across the transistor, activatingthe transistor with control circuitry connected in parallel with thetransistor.
 42. The method of claim 41, further comprising: sensing avoltage below a threshold across the transistor; and upon sensing thevoltage below a threshold across the transistor, deactivating thetransistor with the control circuitry.
 43. The method of claim 41,further comprising: sensing a reverse battery condition with the controlcircuitry; and upon sensing the reverse battery condition, deactivatingthe transistor with the control circuitry.
 44. A power panel comprising:a chassis including a top, a bottom, a front, a rear, and two sides; aplurality of power input connections on the chassis, each power inputconnection including a source input connection and a return inputconnection; a plurality of power output connections on the chassis, eachof the power output connections including a source output connection anda return output connection, and each of the power output connectionsconnected to a power input connection through the chassis; and aprotection circuit connected between at least one of the power outputconnections and a power input connection, the protection circuitincluding: a transistor connected between the return output connectionand the return input connection; and control circuitry electricallyconnected in parallel with the transistor, the control circuitryconfigured to selectively activate the transistor to allow current topass through the transistor based on an observed voltage across thetransistor.
 45. The power panel of claim 44, wherein the plurality ofpower input connections are located on the front of the chassis.
 46. Thepower panel of claim 44, wherein the plurality of power outputconnections are located on modules mounted in the chassis.